Get sum and max in array group by multiple keys

Ruby
1

Having array like this
[
{:id=>2, :idx=>111, :money=>4, :money1=>1, :order=>“001”,
:order1=>“1”},
{:id=>1, :idx=>112, :money=>2, :money1=>2, :order=>“001”,
:order1=>“1”},
{:id=>3, :idx=>113, :money=>3, :money1=>1, :order=>“002”,
:order1=>“2”}
]

After calling method: f_addition(arr, group_fields, sum_fields,
max_fields) (e.x: f_addition(arr, [:order, :order1], [:money, :money1],
[:id, :idx] ). If groups_fields = [], meaning sum all fields in
sum_fields

The result should be:

[
{:id=>2, :idx=>112, :money=>6, :money1=>3,:order=>“001”,
:order1=>“1”},
{:id=>3, idx=>113, :money=>3, ":money1=>1,:order=>“002”,
:order1=>“2”}
]

P/s: the original array should not be changed after calling method (it
is used again as parameter for new group_fields, new sum_fields, new
max_fields)

I am using Ruby 1.8.7 and Rails 2.3.5

Please teach me how to build the method f_addition.

Thanks

2

I suggest you start by explaining what the method is supposed to do.
From your example it is not entirely clear to me. What is the purpose
of each individual method argument and how do they affect the result?